Piston locking device



June l1, 1940. MEYER 2,204,279

PISTON LOCKING DEVICE Filed Nov. 2s, 1958 Patented June 11, 1940 UNITED STATES PATENT OFFICE g PIsToN- LOCKING DEVICE vLudwig Meyer, Dessau, Germany, assgnor to Junkers Flugzeug-und-Motorenwerke Aktiengesellschaft, Dessau, Germany, a corporation of Germany Application November 23, 1938, Serial N0. 242,050 In Germany'November 26, 1937 p 9 Claims.

movement at either or both ends of theirI stroke.

It is an object of the invention to provide a piston locking device comprising locking means carried by the piston to engage the cylinder wall and means mounted in the cylinder for cooperating with the locking means.

Another object of the invention is to provide such a piston ring locking device wherein locking rings are carried by the piston one to engage an annular groove formed in the cylinderwall adjacent each extremity of the cylinder, and resilient actuating means mounted at each extremity of the cylinder one to coact with each locking ring.

A further object of the invention is to provide such-a piston ring locking device wherein one actuating means is so arranged at each extremity of o the, cylinder that it is moved axially by the pressure mediumlby which the piston is subsequently 4moved'to permit release of one locking ring from its cylinder groove before commencement of movement of the piston; and wherein the actuating means remain substantially stationary in the cylinder during the axial movement of the piston and the locking rings carried thereby.

Yet another object of the invention is to pro\ vide such a piston locking device which is rela- 3o tively simple to manufacture and light in weight,

liquid oruid-admitted through one of the cylinder ports I3 or I 3a. Extending from the piston 2 is a piston rod 3.

Around the periphery of thepiston 2 annular grooves I and 5 are formed to receive locking rings 6 and 1 adapted to be expanded to engage annular grooves 8 and-9 respectively formed in the cylinde'wall one vadjacent each extremity of the cylinder I. I will now describe a preferred form of construction. ofthe means provided at the cylinder extremities for expanding thelocking rings 6 and l, which are resilient and tend to contract to a diameter smaller than that of the cylinder bore, and for releasing them to permit them to contract and withdraw from the cylinder grooves 8 and 9 respectively prior to commencement of movement of the piston 2.

Mounted in one extremity of the cylinder I and projecting centrally through one cylinder cover 23 is an annular retainer I2 having an external flange 24 around its inner extremity which is positioned Within the said cover and is held against the inner face of the latter by an annular nut I5, the bore of which is smaller than thatoi the said retainer I2. A plunger I9 extends through the annular nut I5 and terminates at its outer extremity in an enlarged peripheral portion which is axially slidable in the retainer I2. Thus inward movement of the plunger I9 is limited by the nut I5. A packing ring 25 is provided around the periphery of that portion of the 2 plunger I9 which is slidable in the retainer I2 to vprevent leakage, and the plunger is kurged inwardly into the cylinder by a helical spring I0 the outer extremity of which bears against an internal ange carried by the outer extremity ol 4the retainer I2. Formed longitudinally in the outer periphery of the plunger I9 from its inner extremity are a plurality of channels 20.

Similarly an annular retainer I2a, which in this case is apertured for the passage of the piston rod 3 therethrough, projects centrally through the cylinder cover 23a and has an external ange 24a thereon which bears against the inner face ofthe cover 23a and is held thereagainst by an annular nut I5a. The latter similarly limits the inward movement of a plunger Illa the outer extremity of which is axially slidable in the retainer I2a. 25a denotes a packing ring around the plunger to prevent leakagebetween the latter andthe bore of the retainer I2a. Packing rings I1 and 2l are also provided to preventthe escape of the ypressure medium around the rod 3; the ring' I1 is mounted inthe retainer I2a and the ring 21 in the inner extremity of the DlungerISa, which is centrally apertured forthe passage of the said rod therethrough. The plunger Iila'is-urged'inwardl'y into the cylinder by a spring IIla the outer extremity of which is supported by the outer annular portion -of the retainer I2a'through which .the piston vrod 3 slides. a denotes a pluralityof longitudinal channels formed in the outer periphery of the plunger ISa from its inner extremity.

Formed in opposite sides of the piston 2 are concentric recesses I8 and Illa, and extending radially from the latter through passages formed through the said piston are pinsv II land IIa which are adapted to project into the piston grooves 4 and 5 and expand the rings 6 and I respectively. These pins II and Ila have annular grooves 26 and 26a formed around them intermediately of their length into which holding elements 28 and 28a respectively mounted in the piston 2 extend to limit the axial movement of the said pins.

The operation of the locking device is briefly as follows: As the piston 2 reaches the left end of its stroke the plunger I9 enters the recess I8 and contacts the inner extremities of the pins I I. The plunger I9 is then moved axially in the direction of the arrow I4 against the tension of the spring I0 by the piston 2 until the locking ring 6 is in registry with the cylinder groove 8. Then the spring pressed plunger I9 forces the pins II radially outward thereby expanding the ring 6 and moving it into engagement with its groove 8. When it is desired to move the piston 2 in the opposite direction a pressure medium is introduced into the cylinder I through the port I3. This medium flows into the cylinder end I6 and through the channels 20 between the base of the piston recess I8 and the adjacent extremity of the plunger I9, where it exerts pressure upon the latter and forces it outward against the tension or the spring IIl. The locking ring 6, the resilience of which tends to contract it, then withdraws itself from the groove 8 and moves the pins II radiallyinward. The expansion force of the spring IIJ and the contracting force of the rings 6 and 'I bear a denite relationship to the pressure of the Iluid admitted to the cylinder. 'Ihe pressure is so proportioned that it overcomes the force of the spring II) on the one hand, but on the other the force Which it exerts on the rings 6 and 1 is insufiicient to prevent the rings from contracting to their smaller .diameter when the plunger is forced away from the pins I I. As soon as the locking ring 6 disengages the groove 8 the piston 2 is moved towards the opposite extremity of the cylinder where the locking ring 1 is similarly expanded to engage the cylinder groove 9.

The coacting annular inner marginsl of the rings 6 and 'I and the cylinder grooves 8. and 9 may be chamfered as indicated at 2l and 22 to facilitate disengagement of the former from the latter. It will also be noted that the inward movement of the` locking rings 6 and 1 may be regulated as to .distance by the width of the annular grooves 26 and 26a into which the elements 28 and 28a respectively extend.

While in the foregoing the preferred embodi- 'ment of the invention has been shown it is understood that the construction is susceptible to such modications and variations as fall within the scope of the claims.

What`I claim is:

1. A piston locking device comprising a cylinder having an annular groove formed therein, a piston mounted for axial movement therein', a resilient locking ring mounted around the piston for movement therewith adapted to engage said groove and hold the piston immovable, a spring actuated member mounted adjacent one extremity of the cylinder, sliding means extending through the piston in contact with said ring to change its diameter, said sliding means being adapted to be actuated by said member upon movement of the piston, and said spring actuated member being adapted to be moved from said sliding means by a pressure medium admitted into the cylinder to move the piston.

42. A piston locking device comprising a cylinder having an annular groove formed therein, a piston mounted therein, a. resilient locking ring mounted around the piston for movement therewith adapted to engage said groove and lock the piston, a spring actuated member mounted adjacent one extremity of the cylinder, sliding means extending through the piston adapted to expand the ring and force it into engagement with the cylinder groove, said spring actuated member being adapted tomove the sliding means as the piston advances towards said member, said member being adapted to be moved from said sliding means by a pressure medium admitted into the cylinder to move the piston, and said ring being adapted to contract and withdraw from the cylinder groove.

3. A piston locking device comprising the combination set forth in claim 2, wherein means are provided for limiting the movement of the sliding means.

4. A piston locking device comprising a cylinder having an annular groove formed therein, a piston mounted for sliding movement in the cylinder, a resilient locking ring mounted in a groove formed around the piston and adapted to engage the cylinder groove to hold the piston immovable, said piston having a recess formed therein, means mounted for sliding movement through the piston extending from the recess into the piston groove, a spring actuated plunger adapted to enter said recess as the piston is moved, said plunger being adapted to move the sliding means and expand said ring, and means through which a pressure medium is admitted into the recess between the base of the latter and the plunger to move the plunger outwardly and disehgage said sliding means, said ring being adapted to contract and withdraw from the cylinder groove.

5. A piston locking device comprising the com'- bination set forth in claim 4, wherein the plunger and the recess are coaxial with the piston, said sliding means being mounted for radial movement through the piston.

6. A piston locking device comprising the combination set forth in claim 4, wherein the means through which the pressure medium is admitted into the recess consists of longitudinal channels formed in the periphery of. the plunger.

'7. A piston locking device comprising a cylinder having an annular groove formed therein, a cover thereon, a piston mounted for axial movement in the cylinder, a resilient locking ring mounted'in a groove' formed around the piston periphery, adapted to engage the cylinder groove and hold the piston immovable, a spring actuated plunger mounted in said cover, means limiting the movement of the plunger into the cylinder, a recess formed in the face of the piston adjacent the plunger, pins extending from the recess into the ring groove of the piston through the latter,

said plunger being adapted to enter said recess as the piston advances and force the pins outwardly to expand the ring into engagement with the cylinder groove, andmeans through which a pressure medium is admitted between the base of the recess` and the plunger from the cylinder bore to force the plunger outwardly, said ring being adapted to contract and withdraw from the cylinder groove.

8. A piston locking device comprising a cylinder having annular grooves formed therein adjacent its extremities, a. piston mounted for axial movement therein, resilient locking rings mounted in the piston periphery, each ring being adapted to engage one cylinder groove and hold 'J5 the piston immovable, said piston having a concentric recess formed in each face, a spring actuated plunger mounted in each extremity of the cylinder and concentrically therewith, a piston rod extending from the piston projecting through one extremity of the cylinder and through one plunger, radially disposed pins extending through apertures formed in the piston from each recess to the inner periphery of one ring, means limiting the inward movement of said pins, each plunger being -adapted to enter one recess as the piston advances and move the pins extending into said recess axially outward to expand the ring with which they coact and force said ring into engagement with its cylinder groove, and said plungers having longitudinal channels formed in their periphery to permit a flow of a pressure medium into the space between the base of each recess and its cooperating plunger from the adjacent end of the cylinder.

9. A piston locking device comprising, a cylinder having a groove in the wall thereof adjacent one end, a piston mounted for axial movement in the cylinder, a locking mechanism carried by said piston including a part projectible outwardly from the piston and into the groove in the wall of the cylinder when the piston is advancedA to a predetermined position adjacent said end of theA cylinder, a member for actuating said locking mechanism, means mounting said member on the cylinder adjacent said end thereof for limited `movement relative to the cylinder, means for admitting uid under pressure to said end of thev cylinder, said piston and said member both being responsive to such admission of fluid pressure to move in one direction along their respective paths ,of movement, and spring means yieldingly urging said member in the direction opposite to that in which it is urged by said uid pressure, said member having a camming face adapted when the piston approaches said end of the cylinder to engage a part of said locking mechanism and thrust the latter outwardly into the groove in the wall of the cylinder to lock the piston assembly for withdrawal from the groove in the cylinder wall.

LUDWIG MEYER. 

